Day 4 Table of Contents

• Review topics from last week
• Population vs. sample
• Selecting a sample
• Sampling background and activity
• Sampling biases
• Sampling bias background and activity
• Closure

Review

Research Plan

The purpose of the research plan is to lay the groundwork for the activities in the research project. This process will help you anticipate obstacles. Your research plan will include the following sections:

• Introduction
  Statement of problem, review of literature, and hypothesis
• Methods
  Subjects, instruments, materials, structure of study, procedure,
• Data analysis
  Statistical techniques
• Time schedule
  Major activities and completion date in Gantt chart
• Budget
  Projected costs
• Evaluation
  Plans for formal and informal procedures including pilot study

Population vs. sample

The target population is the group to which the researcher would like to generalize his or her results. This defined population has at least one characteristic that differentiates from other groups.

The accessible population is the population to which the researcher has access.

The sample is a portion of the accessible population which will provide representational knowledge or skills held by the population at large.

Practice: What are these three groups in your proposal?

Selecting a sample

Selecting a proper sample is critical if the researcher wishes to generalize the results of the study.

Sampling is the process of selecting a portion of the accessible population in such a way that the individuals represent the target population.

Random sampling ensures all individuals have an equal and independent chance of being selected.

• Best way to obtain representative sample
• Define population, identify each member, and select on a completely chance basis.
• Sample usually selected using a table of random numbers.

Stratified sample is used when subgroups in population need to be equally represented

• in the same proportion that they exist in the population.
• Also to select equal-sized samples from each subgroup if comparisons are desired.
• Same as selecting random group, except done for each subgroup rather than population.

Cluster sampling is when groups, rather than individuals, are selected.

Systematic sampling selects every Kth member, where K equals the number of individuals on the list divided by the number of subjects desired for the sample. Only random if names are random.

Additional information on sampling

Practice your knowledge of sampling techniques.

Sampling biases

Sampling bias is a systematic mistake; the fault of the researcher.

The major source of sampling biases comes from the use of nonprobability sampling techniques. If you can't specify the probability that each member can be chosen, then the results won't be generalizable.

Biases comes from:

• Convenience--because they are readily available,
• Volunteers--probably not like the others who didn't volunteer,
• Judgment sampling--"I think they represent the group,"
• Administrative convenience--when the boss says "use this group."

If a bias does exist, the researcher must describe it fully in the final report.

Sampling bias background and activity will give you practice on these concepts.

Closure; Review and Assignments

Review questions: (To find the answers, click the question mark icon)

• 
  What is the difference between a population and sample?
  What are the different types of populations?
  Why is the selection of a sample so important?
  How do sampling biases occur?
  

Before next week:

• Complete Review of Literature
• Read Chapter 5 in book